A team of researchers from California and New York have found that people infected with the coronavirus may develop lasting immunity, an encouraging discovery for vaccine developers jolted by previous studies indicating human antibodies die out over time.
The study, which has not been peer-reviewed nor published in a scientific journal, found that enough immune cells remain in the body to fight off COVID-19 up to eight months after the initial infection. Scientists say there are signs these virus-fighting capabilities will last for a long time.
The findings, by the Center for Infectious Disease and Vaccine Research at the La Jolla Institute for Immunology and the Icahn School of Medicine at Mount Sinai in New York, provide a major boost to biotechnology companies Moderna and Pfizer, whose promising vaccines have been shadowed by questions about how long coronavirus antibodies stay in the body.
“Indeed, it confirms the study by our group as well as from others (that the human immune response) can be long-lived,” said Nadia Roan, an associate professor at UCSF who has also been studying human immune cells, but was not involved in this most recent study on immunity.
The Moderna and Pfizer vaccines — which have taken the lead in the race for FDA approval — are made with what is known as messenger RNA, or mRNA. They involve the injection of synthetic genetic material that prompts the body to produce proteins — in this case, the “spike” protein that gives the coronavirus its name. The human immune system then makes antibodies to fight the virus proteins.
Pfizer, headquartered in New York City, and its German partner BioNTech released new data Wednesday that showed its vaccine is 95% effective in preventing infections across all races and age groups, including people over age 65. It confirms earlier data that showed 90% efficacy. The news comes a couple of days after Massachusetts-based Moderna announced its vaccine candidate is 94.5% effective, according to preliminary studies.
This remarkable proficiency demonstrated during phase 3 trials wouldn’t mean nearly as much if the antibodies generated by the vaccines fade away over time, leaving people vulnerable again to infection. That’s why the new immunity study is so important.
The research, published on the open access site bioRxiv, which is regularly used by scientists to analyze data, is the most comprehensive study yet of immune memory. The researchers studied 185 men and women, ages 19 to 81, living in California and New York who had recovered from COVID-19. The patients had displayed a range of symptoms from mild to severe.
The transnational team delved deep into the microscopic world of cell memory, tracking B cells, which make antibodies that neutralize pathogens, and T cells, which attack and kill infected cells. The researchers found strong antibodies in most of the subjects six months after they were infected by the coronavirus.
The T cell counts faded slightly, but the B cells actually expanded, leaving enough immune cells in the body to fend off the virus and prevent illness eight months after infection, the researchers said. Eight months was as long as the study lasted, but scientists said the memory cells likely persist longer than that.
“That amount of memory would likely prevent the vast majority of people from getting hospitalized (for) disease, severe disease, for many years,” Shane Crotty, a virologist at the La Jolla Institute of Immunology and co-leader of the study, told the New York Times.
The immune memory cells, however, were not apparent in all the study subjects who contracted SARSCoV-2, the specific coronavirus that causes disease.
“It may be expected that at least a fraction of the SARSCoV-2-infected population with particularly low immune memory would be susceptible to re-infection relatively quickly,” the study warned.
Memory cells have been thrust into the limelight because recent studies indicate the human body may not retain antibodies very long, raising questions about whether permanent immunity to COVID-19 is possible after people recover.
One study showing short-lived coronavirus antibodies was done by King’s College of London, which found antibody levels peaked three weeks after the onset of symptoms and then dramatically declined. A Chinese study published in the June issue of the journal Nature Medicine showed that more than 90% of patients exhibited sharp declines in the number of antibodies within two to three months after infection.
Infectious disease specialists around the world were surprised and discouraged by the rapid reductions observed in the reports, but several other studies, including the one conducted at UCSF, found that the T cell response was detectable for at least 69 days in patients recovering from mild cases of COVID-19.
A Swedish study even found T cells that recognize the coronavirus in patients who had no detectable antibodies.
Roan, an associate investigator at San Francisco’s Gladstone Institutes, said B and T cells that recognize COVID-19 apparently persist in the body and are capable of markedly expanding in number when they detect the pathogen. The new study, she said, bolsters her belief that even small amounts of these memory cells could provide long-term immunity.
“It suggests that COVID-19 doesn't appear to hinder the formation of long-lived memory cells,” said Roan, who recently published a study showing that a protein called Interleukin-7 boosted the number of T cells in the body. “Can a vaccine elicit immunity that can last for years? That's the hope, and theoretically it should be able to, but only time will tell.”
Peter Fimrite is a San Francisco Chronicle staff writer. Email: pfimrite@sfchronicle.com. Twitter: @pfimrite
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November 19, 2020 at 06:31AM
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Does COVID-19 result in lasting immunity? Growing evidence says yes - San Francisco Chronicle
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